The present invention relates to the panoramic optical device and, more particularly, to an optical stack for a panoramic optical device.
Providing high quality optics in a panoramic camera is challenging. Different approaches have been taken for this problem. One approach is to move a lens and to capture a set of images as the lens moves, which cover a field of view over time. The images from the moved lens are combined to form panoramic scene. Another approach is to form an array of multiple different camera lenses and to combine the image results captured by the array of lenses into a single image. Still another is to utilize an ultra-wide angle lens (e.g., a fish-eye lens) to capture a scene with a wider-than-normal field of view. Yet another is to use a panoramic optical device to create a 360 degree horizontal field of view using a single shot (a discrete point of time using a single lens). This later approach is sometimes referred to as a “one-shot” panoramic device, which captures a panoramic scene in a single point in time using a single lens. Each of these approaches has benefits and drawbacks depending on use cases.
Within one-shot solutions that use panoramic optical components, a number of approaches have been taken depending on situation. One approach shown in FIG. 1 (Prior Art) utilizes a hemispherical mirror 120 positioned at the end of a thin post 110. The post 110 sometimes attaches to filter threads of a camera lens. The hemispherical mirror 110 tapers to a point, as it approaches the center of the post 110 to which it is attached. Images captured by this technique are distorted, but can be software corrected using digital signal processing (DSP) techniques.
A different one-shot approach shown in FIG. 2 (Prior Art) utilizes a parabolic mirror 220 connected to a clear spacer 210. The parabolic mirror 220 tapers to a point as it approaches a lens. DSP software/firmware techniques are able to be used to correct for distortions resulting from light being reflected off the parabolic mirror 220.
Conventional panoramic one-shot solutions (such as those shown in FIG. 1 and FIG. 2) are unable to produce high-fidelity (HD) images and are highly restricted in their vertical field of view. An inability to produce high-fidelity images (referring to a 1080-line high definition video (HDV) standard) results in part from an optical scatter from the outwardly expanding mirror. Additional, conventional panoramic one-shot solutions have a horizontal field of view of 360 degrees and a limited vertical field of view. The vertical field of view and fidelity is restricted based on optics of reflecting light from a single hemispherical mirror 120 or off a single parabolic mirror 220 before being captured by a lens/sensor.